Employees can only refuse to work if they believe they are in imminent danger.  The Occupational Safety and Health Act (OSH Act) defines “imminent danger” to include “any conditions or practices in any place of employment which are such that a danger exists which can reasonably be expected to cause death or serious physical harm immediately or before the imminence of such danger can be eliminated through the enforcement procedures otherwise provided by this Act.”  Most workplace environments do not rise to the level that would be considered such that employees would be exposed to imminent danger.  However, if someone refuses to work, the company should investigate and make a determination.